1. Field of the Invention
The present invention relates to the field of valves and more particularly, to remotely controllable automated actuators for plug-type valves.
2. Prior Art
Although the present invention may be suitable for use with a variety of valve types, it is especially adapted for use with the plug-type valve such as disclosed in U.S. Pat. Nos. 3,362,433 and 3,793,893 both issued to Heinen and both currently assigned to Aerojet-General Corporation the assignee of the present invention. The first such issued patent discloses a four-way diverter valve and the second such issued patent discloses a plug-type valve of the double block and bleed configuration which is either opened or closed for either passing or blocking the flow of fluid therethrough. Both such issued patents disclose the use of a handwheel operated actuator and the detailed structure of such an actuator is disclosed in the latter issued patent, the contents of which are incorporated herein by reference. As noted in that later issued patent, the drive shaft to which the handwheel is connected for actuating the valve may, if desired, be instead connected to a suitable power means such as a hydraulic or electric motor. The present invention pertains to such power means which render such valves suitable for automated actuation initiated from a remote location.
Such remotely controllable valve operators are especially useful in oil transferring and processing installations which are often located at great distances from any centers of population. They are also advantageous where such transferring or processing installations are widely dispersed in great numbers and it would be extremely slow, inconvenient and uneconomical to provide on-site manual control each time the status of a valve operator were to be changed such as by opening or closing a valve or by changing the direction of flow through a four way diverter valve.
Such valves are used predominantly in oil fields, petroleum processing plants and other processing industries where inflammable and explosive fluids are found. Therefore, the automatic actuators for such valves typically must have all electrical devices in explosion-proof configurations where any electrically generated spark can at worst produce a limited and contained explosion or fire. Explosion proofing is required to prevent a catastrophic explosion or fire in the environment of fumes where these valves are typically installed. Accordingly, explosion-proof electrical components or containment of non-explosion proof electrical components in explosion proof containers is virtually always an additional requirement that must be met by remotely controllable automatic actuators for such valves.
The most relevant known prior art relating to the present invention comprises an electro-hydraulic valve operator manufactured by Keane Controls Corporation of Fullerton, Calif. The Keane device utilizes a hydraulic motor and a single four-way three-position electrically operated solenoid valve which is exposed to the environment and must therefore be made independently explosion-proof at a substantially increased cost as compared to conventional solenoid valves. The remaining electrical components, consisting of cam-operated switches, are housed in an explosion-proof container. This container is mounted above the top of the valve for mechanical interaction with the valve's operator stem which extends above the valve and is attached to an indicator stem to provide a visual indication of the status of the valve. As a result of having two major separate explosion-proof components, this prior art actuator also requires an expensive copper electrical conduit.
Unfortunately, the Keane device suffers from a number of significant disadvantages which render it more costly to produce and to maintain than the present invention. Furthermore, the Keane apparatus provides a mechanical manual override which is available for manual operation of the valve upon failure of hydraulic and/or electrical power. However, this override feature is inherently unsafe to the manual operator in the event such power is restored while manual override operation is being effected. This significant safety disadvantage is overcome in the present invention as will be hereinafter more fully described. Furthermore, the Keane apparatus fails to provide any dual speed capability, thus requiring single speed valve operation either at an inconvenient and undesirable slow speed or at a undesirable high speed that may eventually result in permanent damage to the valve and/or the process pipeline.